Tank Wastes Planned for On-Site Disposal at Three Department of Energy Sites The Savannah River Site: Interim Report (2005) / Chapter Skim
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II Ideal Objectives and Real-World Challenges
II Ideal Objectives and Real-World Challenges
Pages 21-36
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From page 21... ...
In this section, the committee examines what would be the ideal objectives or end points for the tank wastes and what real-world obstacles make those objectives difficult to achieve. IDEAL OBJECTIVES FOR THE TANK WASTES In an ideal world—that is, if waste retrieval and processing facilities worked ideally and at an acceptable cost—the objectives would be the following: 1.
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From page 22... ...
.33 it is also possible to use acid to dissolve the heels, a method called chemical cleaning. DOE has previously tested several different acids with sludge simulants, tested oxalic acid with real waste, and demonstrated chemical cleaning of a waste tank heel using oxalic acid (Adu-Wusu et al., 2003)
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From page 23... ...
TABLE 2 Tank 16 Waste Removal Process and Curies Removed with Each Sequential Step Cumulative Sequential Waste Curies Percentage Cumulative Percentage Removal Step Removed of Curies Curies Curies Removed Removed Bulk waste removal 2.74 x 106 97 2.74 x 106 97 Spray water washing 2.78 x 104 0.98 2.77 x 106 97.98 Oxalic acid wash and 5.82 x 104 2 2.83 x 106 99.98 rinse SOURCE: (DOE, 2002a) 39 Oxalic acid can also retard hydration of Portland cement, which could reduce the effectiveness of engineered grout as a barrier both in tank grouting and in saltstone if the acid persists.
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From page 24... ...
The waste that is difficult to retrieve tends to be consolidated sludge that has high concentrations of radioactivity, and is difficult to mobilize. Savannah River Site personnel also indicated that a few tanks have zeolite in them.
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From page 25... ...
In addition, sludge waste processing activities result in a net increase in the volume of liquid in the tank system. Also, newly generated waste will continue to be produced by ongoing operations in the H Canyon and other projected missions at the Savannah River Site.
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From page 26... ...
To carry out waste retrieval and other operations, DOE must track the space in the tanks closely and often must make multiple transfers among tanks, and even between tank farms, to ensure that there is sufficient open tank space where needed to support operations. This is a complex problem compounded by the continuing introduction of waste into the tanks.
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From page 27... ...
Tank space crises have loomed at the Savannah River Site for 15-20 years. However, recent actions to free up tank space, including the numerous tank waste transfers across the tank farms, illustrate that available options are diminishing.
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From page 28... ...
, Phase 1: , Interim Processing, ARP/MCU , Step2 |Oper~kd, MoywPplementcoPnbilitlesor l I alone , SWPF tar come wostes | , .- Phase 2: Hiah-Ca~acitv Processing 2004 2006 2000 2010 2012 year T r r . T r 2014 2016 2010 2020 FIGURE 6 Time line for salt waste processing at the Savannah River Site as described by DOE (two-phase, three-step approach)
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From page 29... ...
NOTES: DDA = Deliqulfication, Dissolution, and Adjustment; ARP = Actinide Removal Process; MCU = Modular Caustic-Side Solvent Extraction Unit; SWPF = Salt Waste Processing Facility; DWPF = Defense Waste Processing Facility; SPF = Saltstone Production Facility; SDF = Saltstone Disposal Facility. SOURCE: Adapted from DOE (2005a)
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From page 30... ...
DDA = Deliquificationr Dissolution, and Adjustment; ARP = Actinide Removal Process; MCU = Modular Caustic-Side Solvent Extraction Unit; SWPF = Salt Waste Processing Facility; SPF = Saltstone Production Facility; SDF = Saltstone Disposal Facility. SOURCE: Adapted from DOE (2005a)
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From page 31... ...
higher than the waste from the chemical processes to be used in SWPF. Although DDA generates only 8 percent of the volume of the low-activity waste to be generated during salt waste processing, its waste contains 8090 percent of the total radioactivity that is projected to be sent to the Saltstone Disposal Vaults.43 No separations process is perfect, and using processes that are tailored to the demands imposed by the characteristics of the wastes is, in principle, consistent with the recommendations of a previous National Academies report (NRC, 2000a)
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NOTES: DDA = Deliquification, Dissolution, and Adjustment; ARP = Actinide Removal Process; MCU = Modular Caustic-Side Solvent Extraction Unit; SWPF = Salt Waste Processing Facility. SOURCE: Adapted from DOE (2005a)
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From page 33... ...
For the tanks and their residual waste, DOE plans to fill the tanks with cementitious materials as described in Section I Site personnel have explained that in previous tank grouting, an engineered grout (Smart Grout)
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From page 34... ...
Although highly radioactive waste recovered from a tank could be immobilized for disposal in a repository, exhumed tank pieces and much of the waste from the tank likely would simply be reburied in 48 The regulatory dose limit for an individual worker is 50 millisieverts per year, but DOE has established the DOE control level of 10 millisieverts per year and recommends that facilities adopt a 5-millisievert-per-year administrative control level (DOE, 2004)
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From page 35... ...
Previous National Academies studies have pointed out the pitfalls of such assumptions (NRC, 2000b, 2003, 2005) , noting the likelihood of failure of institutional controls over the long term, even in a location such as the Savannah River Site, which has a continuing national security mission.
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From page 36... ...
approach to protecting human health and the environment from such contaminants differs from that used by the USNRC. The EPA uses a lifetime cancer risk criterion to determine acceptable levels of residual soil contamination, whereas the USNRC and most states use an annual dose criterion.
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